The Sound Science of Sows: Influence of Auditory Environment on Sow Hearing, Piglet Communication, and Sow Behavior in Modern Swine Production

Nichole M Chapel, Purdue University

Abstract

Piglet crushing, the process by which a sow sits on and crushes a piglet to death or causes serious harm, is a grave issue which has caused concern to the swine industry over the past 50 years. Not only does piglet crushing result in over a $1 billion loss in potential revenue for the United States pork industry, but it also results in an estimated 7.5 million dead piglets annually. Prior research has focused on understanding individual sow factors on crushing events (such as the age of sow), however, little focus has been given to the environment. Sow farms can be quite loud, therefore optimizing sow/piglet communication in the current environmental conditions should be given consideration. Many piglet crushing studies utilize restraint piglet vocalizations to test sow reaction, however, none have verified the properties of test vocalizations against actual crushing events. Ten sows were observed 48 h after parturition and crushing events were recorded. If a crushing event occurred, a second piglet within the same litter was used to solicit a vocalization through manual restraint to compare call properties of a restrained call to those of a crushed call. Variables were gathered at the loudest point in a call and as an average across the entire call. Vocalizations were assessed for peak amplitude and frequency variations. Crushed piglets had a lower fundamental frequency and narrower bandwidth when analyzed at the loudest portion of a call ( P < 0.01). Overall, piglets which were crushed had a lower peak frequency and minimum frequency than those which were Restrained ( P = 0.01). No differences were observed for entropy or harmonic to noise ratio between Crushed and Restrained piglets (P > 0.35). In conclusion, differences exist in the call structure between piglets which are crushed from those which undergo restraint. Therefore, restraint vocalizations should not be used as the only stimulus to study a sow’s response to crushing events. Not only is it important to understand the structure of piglet calls, sows must be able to hear the calls in order to respond. Auditory brainstem responses are a method of performing hearing tests on animals to evaluate hearing. These tests are efficient as they can test multiple different components of hearing without requiring the training of animals. The objectives of this study were to successfully complete auditory brainstem responses in pigs, compare hearing in sows to weanling piglets, and observe if older sows have decreased hearing compared to younger sows. Pigs (weaning, n = 7; gilts, n = 5; 2nd and 3rd parity, n = 5; and 5th parity & older, n = 5) were anesthetized and placed in a sound dampening box. Auditory brainstem response (ABR) were performed on clicks at two decibel (dB) levels: 90 and 127 dB sound pressure level. Auditory brainstem responses were analyzed for latency to each wave, amplitude of waves I and V, and distance between waves I-III, III-V, and I-V. Sows in 2nd and 3rd parities had very few distinguishable waves, with only wave I and II present in some sows. Weaning pigs had distinguishable waves I-V at 90 and 127 dB. Overall, hearing impairment and complete hearing loss are occurring in sows raised in mechanical ventilation. Hearing has the potential to impact the welfare of growing pigs and sows, particularly during periods of animal handling or during moments of animal-to-animal communication. Attention should be given to identifying which individuals have decreased hearing ability and the implication on the day-to-day welfare of pigs. Therefore, farrowing sows in an environment which is quiet and better optimized for their hearing ability may be beneficial for a sow’s ability to care for her young...

Degree

Ph.D.

Advisors

Radcliffe, Purdue University.

Subject Area

Agriculture|Animal sciences

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